1. Field of the Invention
This invention relates generally to heating and cooling systems, and more specifically to solar heating and cooling systems for collection, transfer and storage of heat through a change of the liquid/vapor state of a transmission medium.
2. Description of the Prior Art
In the past, non-photovoltaic types of solar heating and cooling systems generally achieved collection, transfer and storage of solar energy either through the change in temperature of a flowing transmission medium which remained in a single liquid or vapor state, or alternatively, through a change in the liquid/vapor state of a flowing transmission medium, acquiring, retaining and remotely releasing the transmission medium's latent heat of evaporation.
The most common such prior art system typically used water as the transmission medium, relied upon the specific heat retention capacity of the transmission medium, and typically required large quantities of the transmission medium to be pumped through a solar collector panel in order that substantial heat transfer takes place.
The above-identified alternative prior art system, in which the more efficient latent heat of evaporation permits a relatively smaller quantity of transmission medium to be pumped through a solar collector, has generally taken the form of "solar-assisted heat pumps". These "solar-assisted heat pumps" are similar in function to conventional heat pumps, in that the solar collector panel served as an evaporator for a compressible transmission medium having a high latent heat of evaporation, such as Freon.RTM. fluorocarbon, wherein a substantial portion of output heat was derived from the electrical energy used in an electromechanical compressor.
In prior-art latent-heat systems, the high pressure liquid transmission medium was usually injected through an expansion valve into a solar collector panel, where the liquid "boiled" or changed state to a gas. The gas was compressed by a conventional mechanical compressor and transmitted to a remote heat exchanger, or "condenser", where heat from the compressed gas was released through the heat exchanger by condensation to a liquid, whereupon the cycle was repeated. In such prior-art latent-heat systems, efficiency was impaired by the occupancy of the solar collector primarily by evaporated gas rather than the denser unevaporated liquid transmission medium.
A substantial portion of the derived heat in such prior art systems came from the relatively costly electrical energy required to operate the mechanical compressor, rather than from the relatively less costly solar radiation. Such prior-art latent-heat-type systems usually incurred substantial heat dissipation within the conventional compressor means, which was ordinarily wasted and not retained as useful delivered heat. Moreover, such prior-art latent-heat-type systems were not amenable to simultaneous refrigeration or cooling of a remote heat exchanger, along with a transfer of solar heat for heating purposes. Such solar-assisted heat pumps required, for refrigeration or cooling purposes that the roles of the solar collector panel and the remote heat exchanger be inverted by a valved reversal of transmission medium flow. Thus, a solar collector panel in such a prior-art system would be required in the refrigeration or cooling mode to become a heat radiator or dissipator which is a mode of operation unlikely to permit efficiency in a solar collector panel upon which solar radiation is impinging.
Prior-art latent-heat type systems usually operated at relatively high pressures, requiring heat exchangers in which the transmission-medium tubing required a small ratio of surface area to volume for mechanical strength and leakage prevention. Consequently, intermediate conduction from the ambient environment to such tubing was necessary through the use of cumbersome, inefficient fins attached thereto.
In prior art latent heat-type systems wherein high-pressure liquid was injected into a solar evaporator, there was no convenient control of the pressure within the evaporator, and hence no convenient control of the temperature within the evaporator at which boiling or evaporation occurred.
A need existed for a latent heat solar heating and cooling system wherein useful heat would be primarily derived from solar radiation, without the wasteful energy consumption of a mechanical compressor.
Another need existed for a latent-heat solar heating and cooling system wherein the ratio of liquid transmission medium to evaporated transmission medium within the solar evaporator would be conveniently controlled to maximize efficiency of solar energy absorption, retention transmission and storage.
Yet another need existed for a latent heat solar heating and cooling system wherein compression, liquification and recovery of latent heat from the transmission medium would not waste or dissipate heat outside the remote heat exchanger.
A further need existed for a latent-heat solar heating and cooling system wherein the role of the solar evaporator need not be reversed from one of solar heat absorption to a less efficient role of dissipation or re-radiation in order to operate in a cooling or a refrigeration mode, and wherein useful remote heating and refrigeration is simultaneously accomplished.
Another need existed for a latent heat solar heating and cooling system wherein efficient heat-exchangers in the solar evaporator have a large ratio of surface area to volume, without danger of leakage or explosion of the transmission medium.
A need also existed for a latent heat solar heating and cooling system wherein the pressure within the solar evaporator and the temperature of transmission medium boiling or evaporation would be conveniently controlled.
Still another need existed for a latent heat solar heating and cooling system wherein full advantage would be taken of the change-of-state of a transmission medium by accomplishing the change-of-state within the solar heat collection means and within the remote heat exchanger.
Yet another need further existed for a latent-heat solar heating and cooling system wherein compression of the transmission medium in a gaseous state would be accomplished without the use of a conventional mechanical compressor, so as to eliminate the energy and heat waste of such conventional mechanical compressor.
Yet a further need also existed for a latent-heat solar heating and cooling system wherein compression of the transmission medium in a gaseous state would be accomplished within a remote heat exchanger, so as to retain all of the heat generated by such compression as useful transmitted heat.
Still a further need existed for a latent-heat solar heating and cooling system wherein cooling or refrigeration would be accomplished simultaneously with the absorption and retention of heat, without reversal of transmission medium flow nor use of the solar collector as a dissipator or re-radiator.
Another need existed for a latent-heat solar heating and cooling system wherein heat withdrawn in the cooling or refrigeration process would be usefully retained or used for desirable heating purposes.
Yet another need existed for a latent-heat solar heating and cooling system wherein the pressure of a transmission medium within tubing, solar collectors and heat exchangers could be low, so as to permit more efficient use of tubing, solar collectors and heat exchangers having a high ratio of surface area to volume.